Micrometer scale components

ABSTRACT

Micrometer scale components comprise a component body comprising an alloy of a first solder metal and a second solder metal, the alloy having a higher liquidus temperature than the second solder metal; and a base region of the structure body wetted to a substrate, wherein the component body has a molded surface profile.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.14/539,728, filed on Nov. 12, 2014, which is a divisional of and claimspriority to U.S. patent application Ser. No. 12/953,311 filed on Nov.23, 2010, issued as U.S. Pat. No. 8,997,832, which are herebyincorporated by reference.

TECHNICAL FIELD

This invention relates to the field of micromanufacturing and morespecifically, to fabrication of micrometer scale components.

BACKGROUND

Energy assisted magnetic recording (EAMR) exploits the drop in amagnetic disk medium's coercivity when the disk's temperature is raisedto near the Curie level. In some EAMR systems, heat from laser light isdirected onto the disk surface via a near-field transducer. Thisrequires micrometer scale components in the write head of the disk thathave good optical properties and good heat resistance to direct thelaser light onto the near-field transducer. Micrometer scale componentsare difficult to manufacture, for example, scales between 20-40 μm aretoo small for traditional machining and too large for photolithographicmethods.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and notlimitation, in the figures of the accompanying drawings in which:

FIG. 1 illustrates a method for manufacturing micrometer scalecomponents according to an embodiment of the invention;

FIG. 2 illustrates an exemplary manufacturing process implemented inaccordance with an embodiment of the invention;

FIG. 3 illustrates a second exemplary manufacturing process implementedin accordance with an embodiment of the invention;

FIG. 4 are SEM images comparing a micrometer scale catoptric structuremanufactured in accordance with an embodiment of the invention to apolymer catoptric structure;

FIG. 5 illustrates a hard drive implemented in accordance with anembodiment of the invention.

FIG. 6 illustrates a EAMR head 220 implemented in accordance with anembodiment of the invention.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth,such as examples of specific layer compositions and properties, toprovide a thorough understanding of various embodiment of the presentinvention. It will be apparent however, to one skilled in the art thatthese specific details need not be employed to practice variousembodiments of the present invention. In other instances, well knowncomponents or methods have not been described in detail to avoidunnecessarily obscuring various embodiments of the present invention.

Embodiments of the present invention include micrometer components andmethods of manufacturing them. In some embodiments, the components havehigh temperature stability, good thermal conductivity, long life, andlow surface roughness.

FIG. 1 illustrates a method for micrometer scale manufacturing accordingto an embodiment of the invention. In step 104, a micrometer scale moldof the structure to be manufactured is formed. In some embodiments, themold is manufactured at the wafer level or chip level. A mold, or arrayof molds, is formed in a substrate, such as glass, epoxy, or metal. Insome embodiments, the mold can be made using a diamond turning withstep-and-repeat process or using a reflow with resistive ion etching(RIE) process.

In the component manufacturing process, a release layer is first applied105 to the mold. In various embodiments, the material for the releaselayer can comprise a metal, such as Au, or other release material suchas polytetrafluoroethylene (PTFE or Teflon). The release layer mayfurther comprise combinations of different materials. In particularembodiments, the release material is determined according to moldmaterial type. For glass and epoxy molds, the release material cancomprise a metal, while for metal molds, the release material cancomprise a polymer such as PTFE. In a particular embodiment, a Aurelease layer is deposited on an epoxy substrate.

In some embodiments, the micrometer scale components are manufacturedattached to a substrate. In some embodiments, the substrate may comprisea holding substrate that will continue to hold the component aftermanufacture, while in other embodiments, the substrate may comprise areleasing substrate configured to allow the component to be removedafter manufacture. In the illustrated embodiment, a first metal coating106 is applied to the substrate and a second metal is deposited 107 inthe mold. In some embodiments, the second metal comprises a soldermaterial while the first metal comprises a metal that the second metalwill wet to and alloy with.

The second metal placed into the mold comprises a metal that is usableas a solder material, for example, the second metal may comprise a lowmelting temperature metal such as In, Sn, Ag, Au, Ge, Ga, Bi, Cu, or Pb,or alloys from alloys systems comprising such elements. In someembodiments, the second metal may be deposited in the mold using thinfilm deposition or electro-plating. In other embodiments, the secondmetal may be placed in the mold as a sphere or other preform shape. Inparticular embodiments, the second metal comprises microspheres coatedwith an oxidation preventing material, such as Au.

In step 108, the first and second metals are alloyed together to formthe micrometer scale component. In some embodiments, the step ofalloying comprises subjecting the mold and substrate assembly to areflow soldering process. For example, the assembly may be reflowsoldered in a forming gas atmosphere to prevent oxidation. In someembodiments, the step of alloying comprises pressing the substrateincluding the first metal coating towards the mold. In addition toensuring complete molding, the step of pressing may crack oxides on thesurface of the solder metal, improving the wetting of the solder metalto the metal coated substrate. The height between the mold and thesubstrate may be controlled by a mechanical stop.

In embodiments, where the release layer is also a metal, the releaselayer itself may alloy with the first and second metals to form thecomponent. The composition and distribution of the manufacturedcomponent may be determined by modifying the various amounts andcompositions of the materials used.

FIG. 2 illustrates a manufacturing process of a micrometer scalecomponent implemented in accordance with an embodiment of the invention.As described above, a micrometer scale mold 115 is coated with a releasematerial 116. In the illustrated embodiment, mold 115 comprises a moldfor a micrometer scale catoptric structure, such as a parabolicreflector. In other embodiments, the mold may comprise a mold forcomponents such as micrometer scale gears, for example for use in flowmeters. After the mold 115 is coated with release layer 116, an assemblycomprising a substrate 118, a first metal 119 coated on the substrate,and a second metal 117 is assembled. In some embodiments, the firstmetal or the second metal comprises In, Sn, Ag, Au, Ge, Ga, Bi, Cu, orPb. In further embodiments, the first and second metal are selected suchthat the second metal 117 wets to and alloys with the first metal 119during a reflow soldering process. In still further embodiments, thefirst metal 119 and second metal 117 are selected such that the alloyformed between the metals has a higher liquidus temperature than thesecond metal. In some embodiments, this allows subsequent temperaturecycling in later manufacturing steps and improved heat resistance duringthe component's lifetime. In embodiments subject to large amounts ofheat, such as laser mirrors, the metals may be selected for theirthermal properties as well.

After an alloying step, the component 120 is formed as an alloy betweenthe metals 117 and 119. In the illustrated embodiment, the substrate andcoating 119 are configured such that after removal from the mold andrelease layer 116, the component 120 retains its attachment to substrate118. In other embodiments, the substrate 118 may be configured torelease the component 120.

In the illustrated embodiment, the component 120 may be exposed tofurther processing steps. For example, if metals chosen for the body donot have the desired reflective properties, a layer of reflectivematerial, such as Au, may be used to coat the substrate 120. In someembodiments, the component 120 comprises a catoptric structure, thecatoptric structure comprising a catoptric face 121 having a parabolicprofile. In particular embodiments, the catoptric face has an area lessthan about 1,000 μm² and a base region 122 of the catoptric structurehas an area less than about 600 μm². The surface roughness of componentsmanufactured in these methods may be very low, for example less thanabout 0.5 microns.

FIG. 3 illustrates an embodiment of the invention utilizing a metalrelease layer. In the illustrated embodiment, release layer 136 is athird metal material that alloys with the metals 117 and 119. In thisembodiment, in addition to wetting with the first metal 119, the secondmetal 117 also wets to the release metal 136. After reflow, thecomponent 130 comprises an alloy of the three metals 117, 119, and 136.In further embodiments, the release material 136 layer or the reflowprocess is configured such that after reflow, the component 130 furthercomprises a substantially pure layer 137 of the third material. This maybe used, for example, to produce a reflective coating on the component130 in a single processing step. For example, metal 136 may comprise Auand after alloying, the component 130 comprises a layer 137 ofsubstantially pure Au that serves as a reflective coating. In particularembodiments, the first and third metals are the same or are from thesame alloy system. For example, the first and third metal may compriseIn, Sn, Ag, Au, Ge, Ga, Bi, Cu, or Pb, or may be selected from alloysystems that include these elements. In a particular embodiment, thefirst 119 and third 136 metals comprise Au and the second metal 117comprises In.

FIG. 4 shows scanning electron microscope (SEM) images of amicrometer-scale parabolic mirror according to an embodiment of theinvention compared to a micrometer-scale polymer based parabolic mirror.The structure 150 was formed using a micrometer scale molding process asdescribed above. A Au release layer on an epoxy mold was used, Au wasused on the substrate, and In was deposited into the release metalcoated mold. The structure 160 was formed using a polymer moldingprocess, after molding, the polymer was coated in Au to form areflective surface. As the Figure illustrates, the catoptric face 151 ofthe mirror 150 is substantially smoother than the face 161 of the mirror160. In particular, large bumps 162 in the face 161 form a rough surfacedue to issues in releasing the polymer from the mold. Additionally, thestructures are prone to puckered formations 163.

FIG. 5 illustrates a hard drive 200 implemented in accordance with anembodiment of the invention. Hard drive 200 may include one or moredisks 210 to store data. Disk 210 resides on a spindle assembly 260 thatis mounted to drive housing 280. Data may be stored along tracks in themagnetic recording layer of disk 200. The reading and writing of data isaccomplished with head 220 that has both read and write elements. Thewrite element is used to alter the properties of the perpendicularmagnetic recording layer of disk 200. In one embodiment, head 220 mayhave magneto-resistive (MR), or giant magneto-resistive (GMR) elements.In an alternative embodiment, head 220 may be another type of head, forexample, an inductive read/write head or a Hall effect head. In theillustrated embodiment, the hard drive 200 is a heat or energy assistedmagnetic recording (EAMR) drive and incorporates components of a lasersource, a mirror of the type described above, and a near-fieldtransducer (not depicted). Techniques in generating and focusing a laserbeam are known in the art, and thus, are not described in particulardetail. A spindle motor (not shown) rotates spindle assembly 260 and,thereby, disk 200 to position head 220 at a particular location along adesired disk track. The position of head 220 relative to disk 200 may becontrolled by position control circuitry 270.

FIG. 6 illustrates a EAMR head 220 implemented in accordance with anembodiment of the invention. A laser 300 shines a diverging laser beam301 onto the catoptric surface of a catoptric structure 303. In theillustrated embodiment, the catoptric structure comprises a parabolicmirror. The diverging laser light 201 is collimated by the catoptricstructure 303 to form a collimated laser beam 302. The collimated laserbeam is directed by the catoptric structure 303 onto a waveguide 304,for example, onto a grating disposed on the waveguide 304. Waveguide 304transmits the laser energy to near field transducer 305. The near fieldtransducer focuses the laser energy to a spot on the disk 200, heatingthe disk to reduce its coercivity and assist in magnetic recording.

In the foregoing specification, embodiments of the invention have beendescribed with reference to specific exemplary features thereof. Itwill, however, be evident that various modifications and changes may bemade thereto without departing from the broader spirit and scope of theinvention as set forth in the appended claims. The specification andfigures are, accordingly, to be regarded in an illustrative rather thana restrictive sense.

What is claimed is:
 1. A micrometer scale component, comprising: acomponent body comprising an alloy of a first solder metal and a secondsolder metal, the alloy having a higher liquidus temperature than thesecond solder metal; and a base region of the component body wetted to asubstrate, wherein the component body comprises a catoptric structurehaving a catoptric face with a parabolic profile.
 2. The micrometerscale component of claim 1, wherein the alloy comprises a heat sinkmaterial.
 3. The micrometer scale component of claim 1, wherein thecatoptric face has an area less than about 1,000 μm² and the base regionhas an area less than about 600 μm².
 4. The micrometer scale componentof claim 1, wherein the component body further comprises a surface layerof a third metal, and wherein the alloy comprises an alloy of the firstsolder metal, the second solder metal, and the third solder metal. 5.The micrometer scale component of claim 1, wherein the first soldermetal and the second solder metal comprise In, Sn, Ag, Au, Ge, Ga, Bi,Cu, or Pb.